Calcium sulfoaluminate (CSA) cements generally comprise cements containing the components 4CaOxc2x73Al2O3xc2x7SO3, CaSO4, and CaO. When CSA cements are hydrated, ettringite is formed by the following reaction:
4CaOxc2x73Al2O3xc2x7SO3+8CaSO4+6CaO+93H2Oxe2x86x923(CaOxc2x7Al2O3xc2x73CaSO4xc2x731H2O)
The formation of ettringite is very fast. This reaction provides for high early compressive strength of a cementitious formulation; however, this reaction causes the loss of workability of the cementitious formulation. To slow down the reaction and provide increased workability, retarders have been added to slow the hydration reaction in CSA cements. Typically, the retarders chelate the calcium and thus slow the hydration reaction.
U.S. Pat. No. 3,860,433 to Ost et al. discloses sucrose, boric acid, or mucic acid as retarders for calcium sulfoaluminate cements.
U.S. Pat. No. 3,973,978 to Nakagawa et al. discloses a calcium aluminate cement in combination with an organic sulfate that is retarded by organic carboxyic acids, such as gluconic acid, tartaric acid, salicylic acid, citric acid, malic acid, and the sodium, potassium, or lithium salts these acids either alone or in combination with a carbonate or a hydroxide.
U.S. Pat. No. 4,190,454 to Yamagisi et al. discloses a calcium aluminate cement in combination with an organic sulfate that is retarded by a combination of carboxylic acids with an alkali carbonate. The retarder composition being i) gluconic acid and/or tartaric acid and/or s water soluble salt thereof; ii) citric acid and or an alkali salt therof; and iii) an alkali carbonate.
U.S. Pat. Nos. 4,286,992 and 4,286,991 to Galer et al. disclose a retarder for calcium sulfoaluminate cements being a hydroxy polycarboxylic acid in combination with either sucrose or a starch hydrolyzate. The hydroxy polycarboxylic acids can be citric acid, tartaric acid, malic acid or mucic acid.
U.S. Pat. No. 4,670,055 to Koslowski discloses a retarder for calcium sulfoaluminate cements that is a combination of calcium sulfate with an organic setting retarder for aluminate, such as a hydroxy carboxylic acid, such as citric acid, tartaric acid, or malic acid.
U.S. Pat. No. 4,798,628 to Mills et al. discloses a modified formulation of a calcium sulfoaluminate cement. This cement can be retarded with citric acid.
U.S. Pat. No. 5,481,061 to Funabashi et al. discloses improving the fluidity of a calcium sulfoaluminate cement by incorporation of a hydrophilic material, such as a salt of a polybasic carboxylic acid.
JP 1289890 discloses a calcium sulfoaluminate and portland cement mixture that is retarded with a hydroxycarboxylic acid or its salt, such as citric acid.
EP 856495 discloses a gypsum and ettringite cement that can optionally contain a retarder being tartaric acid with up to 2 wt. % calcium hydroxide.
EP 579063 discloses a calcium sulfoaluminate and calcium silicate cement that contains a calcium sulfoaluminate cement retarder being a hydroxy carboxylic acid, such as tartaric acid or citric acid, or it water-soluble salts.
GB 1506417 discloses a calcium sulfoaluminate cement retarded by boric acid, carboxylic acids, such as citric acid or alpha-ketoglutaric acid, keratin, or cellulose.
While it has been known to use carboxylic acids, such as citric acid or tartaric acid, for retarders in calcium sulfoaluminate cements, these carboxylic acids require a large dose to be effective at retarding the reaction. At higher doses, not only is the set retarded, but the compressive strength of a resulting cement is reduced. Increased workability is achieved at the cost of decreased compressive strength.
To overcome the problems with decreased compressive strength, carboxylic acids have been used in combination with other additives to recapture some of the lost compressive strength. U.S. Pat. No. 4,190,454, U.S. Pat. No. 4,286,991, U.S. Pat. No. 4,286,992, U.S. Pat. No. 4,670,055, and EP 579063 above disclose combinations that try to recapture the compressive strength.
It has also been known to use phosphono butane tricarboxylic acids and phosphono aliphatic carboxylic acids as set retarders (U.S. Pat. No. 5,398,759 to Rodrigues et al.) and flow improvement aids (U.S. Pat. No. 4,040,854 to Persinski et al.) for oil and gas well cements. However, the use of phosphono alkyl carboxylic acids as a retarder for calcium sulfoaluminate cements has not been previously known.
What is needed in the industry is a set retarder for calcium sulfoaluminate cements that retards the set of the cement without a significant reduction in the compressive strength of a resulting cement.
It is therefore desirable to provide an admixture that retards the hydration of calcium sulfoaluminate cements without a significant reduction in the compressive strength of the cement.
It is also desirable to provide a calcium sulfoaluminate cement formulation containing a retarder that retards the hydration of the calcium sulfoaluminate cement without a significant reduction in the compressive strength of the cement.
A cementitious formulation is provided comprising a calcium sulfoaluminate cement and a retarder, that develops a 2 hour compressive strength greater than about 2000 pounds per square inch, wherein the retarder comprises a component being at least one of a phosphono alkyl carboxylic acid and a salt of a phosphono alkyl carboxylic acid. Additionally, the retarder can comprise at least one of a carboxylic acid and a salt of a carboxylic acid.
Also provided is a method of retarding the set of a calcium sulfoaluminate cementitious formulation without substantially reducing achievable compressive strength, comprising providing in said cementitious formulation, a retarder comprising a component being at least one of a phosphono alkyl carboxylic acid and a salt of a phosphono alkyl carboxylic acid, and wherein the calcium sulfoaluminate cementitious formulation comprises a calcium sulfoaluminate cement; and adding water to said cementitious formulation to cause the cementitious formulation to set, developing a 2-hour compressive strength of greater than about 2000 pounds per square inch.